The influence of crystal morphology on the process of positronium formation in docosane. The accessibility of electrons for trapping

Various morphologies of docosane crystals have been obtained by crystallization of samples of the same origin with different methods. The positron annihilation lifetime spectra indicate some differences between them, which are related to the differences in the electron trapping capability. To find out the origin of these differences, some crystallographic and optical spectroscopic studies were performed. We argue that the differences in each structure are related to the ease of electron release from traps during excitation and not only to the density of the traps, as has been assumed so far.